The present invention relates generally to a method for making a film with a higher surface energy having improved wettability properties.
Condensing heat exchangers are employed in condensing furnaces to increase efficiency. The condensing heat exchanger cools the heating fluid to a temperature below the dew point. As the temperature drops below the dew point, a liquid condensate, water vapor, condenses from the heating fluid. As the liquid condensate condenses, heat is transferred from the water vapor to the air to be heated. As more heat is produced, the efficiency of the system is increased.
Polypropylene films are used to make laminated heat exchanger material. Most films have surface energies (30-40 dynes) that are considerably lower than the surface energy of water (78 dynes). Because the films have a considerably lower surface energy, the liquid condensate forms as droplets on the surface of the film, rather than spreading out as a thin film. The droplets can leave the film and enter the atmosphere. As the liquid condensate is slightly acidic, the formation of droplets is environmentally undesirable.
Liquid condensate also forms as droplets on air conditioner evaporator heat exchanger fin stock. The film applied to the aluminum fin is also of low surface energy. As air flows, the liquid condensate droplets can leave the surface of the film and enter the area which is to be cooled. Additionally, the droplets can increase the likelihood of corrosion of the fins.
Hence, there is a need in the art for a method for making a film with a higher surface energy having improved wettability properties.